Previously, there is a network system where a plurality of equipment which provides various services is connected to each other via a network. For example, above mentioned network system is disclosed in Japanese Patent Publication JP 9-139742 A. Above mentioned equipment is, such as, a lighting device which provides a lighting control or a lighting monitoring as services, a air conditioner which provides an air conditioning control or an air conditioning monitoring as services, and a locking device which provides a locking control or a locking monitoring as services.
Each of the equipment has one or more objects for executing each service. Each of the equipment executes the object upon receiving a service request (an execution request) with a specific identifier which is assigned to each of the objects, thereby performing an operation corresponding to each service.
In the above mentioned network system, one equipment sends the service request to the other equipment when an event occurs, and a client terminal connected to the network sends the service request to a particular equipment. Above mentioned service request is sent on the basis of a correspondence relation between each of the equipment and the specific identifier assigned to the object which each of the equipment have. That is, the equipment and the client terminal, which make the service request, have the particular equipment execute a particular service with reference to the correspondence relation between the equipment and the specific identifier.
Establishing communication by the use of the connection protocol in such network system enables addition or deletion of the terminal, and communication control or management reflecting address modification, because a gateway always recognizes address information or connection information of all terminals.
However, when the equipment is associated with the specific identifier by the use of the connection information of the connection protocol, each of the terminals should establish a connection (a path to the other terminal) before communication, and the gateway should maintain the connection to all of the terminals connected thereto. Such communication requires excess resources.
By contrast, using a connectionless communication reduces resources necessary for communication. However, it is difficult for the connectionless communication to make addition or deletion of the terminal, and communication control or management reflecting address modification. The connectionless communication is improper to communication using the association between the equipment and the specific identifier.